![]() ![]() ![]() Interestingly there is an equilibrium of forces in the complete system even when we accelerate the earth is drawn towards us by the same force by which we are drawn to the earth, and it accelerates (ever so minutely) towards us, preserving the earth+man system's momentum. In water the friction is much stronger and the terminal velocity will be much smaller. For a person falling through air that's the terminal velocity, about 250 km/h. From then on it will move with constant velocity because no net force is exerted on it any longer. In other words, every force involves the interaction of two objects. This is a better way to say it: A force is exerted by one object on another object. Why then does a box move when I push it Shouldnt the two opposing forces. Everyone knows that every action has an equal and opposite reaction, right Unfortunately, this statement lacks some necessary detail. We accelerated when we started to sink in, and then there indeed was a net force (because the soft sand or fluid was giving and could not carry us) as is required for acceleration.īut what happens once we have started sinking in? In fluids and probably in quicksand (which I assume behaves similar to a fluid) the friction increases with velocity at some point a body moving through it will encounter an amount of friction which cancels out its weight. According to Newtons third law, every action has an equal and opposite reaction. In fact, Newtons's First Law forbids a force difference. And not on an exact description of a non-linear motion.Ī uniform motion (like sinking into quicksand with constant speed) does not require a net force the force onto our foot soles touching the sand exactly counteracts our weight. Of course, but the point of this answer is to make the distinction between on whom the forces act. That's why the sand moves away.ġ: This is not the correct physical formulation constant speed, no force, blabla. On the other hand, it is of course true that we exert the same force as the sand exerts on us on the sand. Well, we don't fall but the sand $brakes^1$ our motion, so it certainly exerts a force on us but less than the earth does on us! No one ever said, that the force of the earth on us is the same as the force of the sand on us (remember: the law speaks of two forces on two different bodies). Because action and reaction forces are applied on different bodies. Like the sun on the earth and vice versa). So your conclusion may be: If the earth pulls on us, we pull on the earth (via gravity! Not via "pushing with out feets". We have two forces on two different bodies. This Law states that every action force and reaction force are equal and opposite. So: force on B from A = - force on A from B. This idea was proposed by Sir Isaac Newton and is his Third Law Of Motion. The extent of revision required to make the "law" even vaguely scientific demonstrates how unscientific the original was.If body A exerts a force on body B, then body B exerts a force (equal in magnitude but opposite direction) on body A. The modernized version of the law is "When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body." There is no empirical basis for this "law" and it makes no sense at all unless taken as a principle based on established authority. It could also be pointed out that the "law" itself is just metaphysical twaddle. Whatever you do to others will be done to you.Īnd then that moral law is generalized to all things to make the physical law:įor every action there is an equal and opposite reaction.Īlso, it could be argued that the use of actio ( ) implies a rational agent, not an abstract principle. If the golden rule is: do unto others as you would have them do unto you and you restate that as if it has force of law then you get: Translation from google: "To every action there is always opposed an equal reaction" ![]() Newton's third law is: "Actioni contrariam semper et æqualem esse reactionem" ![]()
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